some of them wear heavy for more pdef and less dmg.u will see in IL daggers with IC and IC shield and with reflect bufs,such a pain in the ass.thats so wrong but the game let you choose u want to run faster and hit faster and move cooler what so ever ,than wear light,u want to be alive more to reflect dmg to hit slow etc etc,wear heavy.as for archers they wear heavy for p.def and p.atk and very low evasion and acc....
i wear light on both class and with my light i kill any archer/dagger in heavy